Exercise alone reduces insulin resistance in obese children independently of changes in body composition

Context: The number of obese children with insulin resistance and type 2 diabetes is increasing, but the best management strategy is not clear. Objective: The objective of this study was to assess the effect of a structured 8-wk exercise training program on insulin resistance and changes in body composition in obese children. Design: The study was 8 wk of structured supervised exercise intervention with outcome measures before and after the exercise period. Subjects: Fourteen obese children ( 12.70 +/- 2.32 yr; eight male, six female) with high fasting insulin levels were enrolled into the study. Intervention: Intervention consisted of 8 wk of supervised circuit-based exercise training, composed of three fully supervised 1-h sessions per week. Outcome Measures: Outcome measures were assessed pretraining program and posttraining program and included insulin sensitivity ( euglycemic-hyperinsulinemic clamp studies), fasting insulin and glucose levels, body composition using dual energy x-ray absorptiometry scan, lipid profile, and liver function tests. Results: Insulin sensitivity improved significantly after 8 wk of training (M-lbm 8.20 +/- 3.44 to 10.03 +/- 4.33 mg/ kg.min, P < 0.05). Sub-maximal exercise heart rate responses were significantly lower following the training ( P < 0.05), indicating an improvement in cardiorespiratory fitness. Dual energy x-ray absorptiometry scans revealed no differences in lean body mass or abdominal fat mass. Conclusion: An 8-wk exercise training program increases insulin sensitivity in obese children, and this improvement occurred in the presence of increased cardiorespiratory fitness but is independent of measurable changes in body composition.